Did you do it with the iPOD plugged into the USB port? Also, does your computer go into Stand By mode or Hibernation? Try disabling power management or do it to the USB hub specifically:
Click Start, and then click Run. Type devmgmt.msc in the Open box, and then click OK. Expand the Universal Serial Bus controllers and then follow these steps for each USB Root Hub that is listed: Right-click the USB Root Hub, and then click Properties. Click the Power Management tab. Click to clear the "Allow the computer to turn off this device to save power" check box, and then click OK.